In modern critical care/intensive care environments, it is necessary to monitor various hemodynamic functions over extended periods of time. For instance, the amplitude and shape of blood pressure wave formations within various portions of the human cardiovascular must be assessed, such as right atrium and ventricle pressures, pulmonary arterial/pulmonary wedge pressures, systemic arterial pressures, and the like. Conventional monitoring systems, such as are disclosed in U.S. Pat. Nos. 3,675,891 and 4,192,303, include an indwelling catheter connected to a transducer, which in turn is connected to a pressure monitor. The fluid-filled catheter and connecting tubing transmit the mechanical energy of the cardiovascular waveform to a diaphragm of the pressure transducer. The movement of the diaphragm in turn effects variation in an electrical function which is transformed by an amplifier to a visual display on an oscilloscope or strip chart recorder. In order to allow reliable functioning of the system over long periods of time, it is necessary to provide a continuous regulated small-volume flow of a blood anticoagulant (such as heparin) or like medical fluid to prevent occlusion of the intravascular end of the catheter by blood coagulation. A large-volume flushing flow of fluid is necessary to establish fluid within the system when setting up, or to flush clots or air bubbles should they occur during monitoring.
While prior art assemblies have functioned generally satisfactorily, there have been a number of drawbacks associated therewith. For instance, some flow regulating assemblies have had excessive turbulence and air bubble entrapment associated therewith, necessitate the use of both an operator's hands when fast flushing, differential seatings of the valve being provided before and after fast-flush (resulting in a variance of the small-volume flow rates), quality control problems during fabrication, inability to provide adjustment of the small-volume flow rate from the exterior of the assembly, inability to re-use the assembly, and relatively expensive resistor designs. Further, as indicated by Schwartz et al in the March-April 1977 issue of Critical Care Medicine in an article entitled "A Hazard of the Intraflow Continuous System", occasional false high pressure recording due to the pressure head in the flush container affecting transducer readings can occur.
According to the present invention, a flow regulating assembly and components therefor, and a method of facilitating control of a flow in a catheter system for monitoring hemodynamic functions, are provided that eliminate all of the above-mentioned drawbacks. According to the present invention, it is possible to fit components of the flow regulating assembly together without gluing or welding so that the assembly may be cleaned after use and re-used, it is possible to adjust the flow rate of the regulated small-volume flow, turbulence and air entrapment are minimized by providing a straight-through large-volume flush and movement of the flow occluder completely out of the fluid flow path, and operation can be effected with only one hand. The assembly components are simple and easy to manufacture, and the entire system is relatively inexpensive yet provides improved operation.
According to one aspect of the present invention, a flow regulating assembly for providing a continuous regulated small-volume flow of a medical fluid to a a catheter system for monitoring hemodynamic functions and for providing an intermittent operator-controlled large-volume flushing flow of the fluid to the catheter system is provided. The assembly comprises a housing, a fluid inlet passage to the housing, and a fluid outlet passage from the housing directly intersecting with the fluid inlet. A fluid flow-occluding member is mounted in the housing for movement from the first position generally at the intersection of the inlet and outlet wherein flow between the inlet and outlet is occluded, to a second position completely out of the path of fluid flow so that a flushing flow of fluid from the inlet to the outlet takes place. A restricting passageway is defined in the flow-occluding member so that when the member is in the first position a small-volume continuous regulated flow of fluid from the inlet through the occluding member to the outlet takes place. The flow-occluding member is mounted for reciprocal movement from the first position to the second position, with the path of reciprocal movement preferably making an angle of about 30.degree.-60.degree. with the inlet.
According to another aspect of the assembly according to the present invention, the flow-occluding member actuating means is mounted exteriorly of the housing, and the restricting passageway in the flow-occluding member is defined by a small inlet passage to the flow-occluding member, a small outlet passage from the flow-occluding member (the inlet and outlet passageways intersecting in the flow-occluding member) and a needle-valve means distinct from the flow-occluding member disposed at the intersection between the small inlet and outlet passageways for providing a restriction between the small inlet and outlet passageways. The valve means preferably is provided by a screw having a conical tip and positioned concentric with the flow-occluding member and reciprocal in the same path as the flow-occluding member, and with respect to the flow-occluding member. Adjustment of the needle-valve screw is provided from the exterior of the housing by simple utilization of a screwdriver.
According to another aspect of the present invention, a valve element for use in the flow regulating assembly is provided. The valve element includes an elongated piston having a first end portion and a second end portion with a first sealing member exterior of the piston member first end portion and a second sealing member exterior of the second piston member second end portion. A central passageway is defined in the piston member from the first end to the second end thereof generally parallel to the dimension of elongation of the piston member. A fluid inlet passageway is defined in the piston member between the first and second sealing members and intersecting the central passageway, so that fluid entering the inlet passageway between the sealing members in the dimension of elongation of the piston may flow into the central passageway. The element further comprises a needle-valve means and means for mounting the needle-valve means in the central passageway on the opposite side of the fluid inlet as the second sealing member and at the intersection between the inlet passageway and the central passageway for providing a fluid restriction between the inlet passageway and central passageway. A screw with a conical tip provides the needle-valve means and preferably the central passageway has a large diameter than the piston member first portion than in the second portion.
A method of facilitating control of a flow for providing a continuous regulated small-volume flow or an intermittent operator-controlled large-volume flushing flow of a medical fluid to a catheter system for monitoring hemodynamic functions is also provided according to the present invention. The method includes the steps of (a) sterilizing the assembly components and (b) fitting the assembly components together in a clean room to provide a sterile complete assembly, without welding or gluing of the components. The method further comprises the steps of sequentially (c) operatively connecting the assembly to a catheter system, flush container, and transducer; (d) operating the assembly to provide a large-volume flushing flow of fluid; (e) unconnecting the assembly from the catheter system, flush container, and transducer; and (f) repeating steps (a), (b) and (c) using the same assembly components. The method also comprises the further step of, after step (c), (g) effecting adjustment of the volume of the continuous regulated small-volume flow from exteriorly of the assembly housing and without affecting the sterility of the assembly.
It is the primary object of the present invention to provide a simple and effective assembly, components, and method adapted to provide a continuous regulated small-volume or an intermittent operator-controlled large-volume flushing flow of a medical fluid to a catheter system for monitoring hemodynamic functions. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.